Inert gas shielding for rapid solidification apparatus

ABSTRACT

A rapid solidification apparatus is provided. The rapid solidification apparatus includes a movable chill body defining a quench surface, a molten material nozzle for directing one or more streams of molten material towards the quench surface and a source of inert gas. The source of inert gas is configured to provide a conical shield of pressurized inert gas around the one or more streams of molten material. The conical shield extends from the molten material nozzle towards the quench surface with focal point of the conical shield at or proximate the quench surface.

TECHNICAL FIELD

The present disclosure relates to a rapid solidification apparatus. In particular, the present disclosure relates to an inert gas shielding for a rapid solidification apparatus.

BACKGROUND

Rapid solidification process such as melt spinning or other similar processes are used for manufacturing thin foils or flakes of rapidly solidifying alloys or other materials for industrial applications such as powder metallurgy. In the rapid solidification process a stream of melted alloy or other material is ejected onto a moving cold surface to form a thin foil or flake.

A problem that occurs in the rapid solidification process is that of oxidation of the molten material. Oxidation may cause inclusions and bonding issues during consolidation and leads to inferior quality of the end product.

Conventional methods overcome the problem of oxidation of molten material by carrying out the rapid solidification process in an apparatus that includes a vacuum chamber. However, such rapid solidification apparatus that includes a vacuum chamber are difficult to operate and maintain.

U.S. Pat. No. 4,664,176 discloses an apparatus for casting smooth metal strips. The apparatus disclosed in this document includes a moving chill body having a quench surface and a nozzle means for depositing a stream of molten metal on a quenching region of the quenching surface to form the strip. The apparatus further includes a means for supplying a low density, high temperature gas to a region located adjacent to and upstream of the quenching region to provide a low density atmosphere.

U.S. Pat. No. 4,262,734 discloses an apparatus which provides gas jets that encompass and are coaxial with a ejected melt stream. The coaxial gas jets bears down on and surround a melt puddle formed by the ejected melt stream for reducing edge defects in rapidly quenched amorphous strips.

SUMMARY OF THE INVENTION

The present disclosure provides for a rapid solidification apparatus. The rapid solidification apparatus includes a movable chill body defining a quench surface, a molten material nozzle for directing one or more streams of molten material towards the quench surface and a source of inert gas. The source of inert gas is configured to provide a conical shield of pressurized inert gas around the one or more streams of molten material, the conical shield extends from the molten material nozzle towards the quench surface with focal point of the conical shield at or proximate the quench surface.

In yet another aspect, a method of rapidly solidifying a molten material is disclosed. The method includes directing one or more streams of molten material from a source of molten material towards a moving chill body defining a quench surface. The method further includes providing a conical shield of pressurized inert gas around the one or more streams of molten material, the conical shield extending from the molten material nozzle towards the quench surface with the focal point of the conical shield at or proximate the quench surface.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a rapid solidification apparatus in accordance with an embodiment.

FIG. 2 illustrates a rapid solidification apparatus in accordance with an alternate embodiment.

FIG. 3 illustrates a rapid solidification apparatus in accordance with an alternate embodiment.

FIG. 4 is a flow chart illustrating a method of rapidly solidifying a molten material in accordance with an embodiment.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

The present disclosure relates to a rapid solidification apparatus. FIG. 1 illustrates an exemplary rapid solidification apparatus 100. The rapid solidification apparatus 100 includes a movable chill body 102, a molten material nozzle 104 and a source of inert gas 106. The movable chill body 102 is configured to move at a predefined speed in a direction indicated by the arrow 109 and defines a quench surface 108. The molten material nozzle 104 is configured for directing one or more streams of molten material 110 towards the quench surface 108. The source of inert gas 106 is configured to provide a conical shield 116 of pressurized inert gas around the one or more streams of molten material 110 that extends from the molten material nozzle 104 towards the quench surface 108.

In accordance with an aspect, the movable chill body 102 may be a chill roll that comprises of a cylindrical body having the quench surface 108 at its circumferential surface. The chill roll may be configured to rotate at a predefined speed. The chill roll may be internally cooled with a cooling fluid. Alternatively, the quench surface 108 of the chill roll may be cooled by spraying the quench surface 108 with the cooling fluid. Cooling fluid may be water or any other suitable cooling fluid.

Alternatively, the movable chill body 102 may comprise of a roller and belt assembly. In such embodiment, the quench surface 108 is in the form of a belt that is configured to move at a predefined speed between two or more rollers. Either the rollers or the belt in such embodiment may be cooled with a cooling fluid such as water or any other suitable cooling fluid.

Referring again to FIG. 1. the rapid solidification apparatus 100 includes the molten material nozzle 104 directed towards the movable chill body 102. The molten material nozzle 104 is configured for directing the one or more streams of molten material 110 towards the quench surface 108. The molten material nozzle 104 may comprise of a reservoir 112 for holding the molten material and one or more molten material orifice 114 in fluid communication with the reservoir 112 for ejecting the molten material to form the one or more streams of molten material 110. The molten material nozzle 104 may further include a heating means for heating the material to a molten state or for maintaining the material in a molten state. The molten material nozzle 104 may further be equipped with means for pressurizing the molten material in the reservoir 112 such that molten material is directed towards the quench surface 108 as a pressurized stream of molten material 110. The molten material in the reservoir 112 may be pressurized by means of gas pressure, head pressure of the molten material or the like for controlling molten material flow. The molten material nozzle 104 may further include a stirrer or similar means for stirring the molten material for material uniformity. In an alternate embodiment, there may be a plurality of molten material nozzles 104. The molten material nozzle 104 may be made of any suitable inert material that does not react with the molten material and can withstand high temperature.

The source of inert gas 106 is configured to provide a conical shield 116 of pressurized inert gas around the one or more streams of molten material 110. The conical shield 116 completely surrounds the one or more streams of molten material 110. The source of inert gas 106 may be a plurality of gas nozzles 120. Each of the plurality of gas nozzles 120 has a gas orifice 121 for providing a stream of pressured inert gas. The plurality of gas nozzles 120 together provides the conical shield 116 of pressured inert gas. Alternatively, the source of inert gas 106 may be an angled nozzle ring (not shown). The angled nozzle ring may have a number of orifice through which pressurized inert gas may be provided to form the conical shield 116 of pressurized inert gas. Alternatively, the angled nozzle ring may have a single ring shaped orifice through which pressurized inert gas may be provided to form the conical shield 116 of pressurized inert gas.

The conical shield 116 of pressurized inert gas extends from the molten material nozzle 104 towards the quench surface 108 with focal point 118 of the conical shield 116 proximate the quench surface 108. In the embodiment shown in FIG. 1 the conical shield 116 has focal point 118 just before the quench surface 108 of the movable chill body 102. In an alternate embodiment (not shown), the conical shield 116 has focal point 118 at the quench surface 108 of the movable chill body 102.

In accordance with an embodiment, the conical shield 116 has a focal point 118 upstream of the point of contact between the molten material and the movable chill body 102. In such embodiments, the source of inert gas 106 is placed off center with respect to the molten material nozzle 104. The focal point in such an embodiment is a focal line.

In an embodiment, the source of inert gas 106 may be attached to the molten material nozzle 104. As illustrated in FIG. 1 the plurality of gas nozzles 120 are attached to the molten material nozzle 104. Alternatively, the source of inert gas 106 may be placed at a point away from the molten material nozzle 104. As illustrated in FIG. 2 the plurality of gas nozzles 120 are placed at a point away from the molten material nozzle 104 and in between the molten material nozzle 104 and the movable chill body 102. Where the source of inert gas 106 is not attached to molten material nozzle 104 the source of inert gas 106 is configured to direct pressurized inert gas towards the molten material nozzle 104 and the movable chill body 102. As illustrated in FIG. 2, the gas nozzle 102 further comprises a second gas orifice 202 for directing the pressurized inert gas towards the molten material nozzle 104. The source of inert gas 106 is configured to pressurize the inert gas. In another embodiment, an external compressor (not shown) may be used for pressurizing the inert gas. In such embodiments, the external compressor is in fluid communication with the source of inert gas 106. In an embodiment, the pressure of the inert gas is greater than or equal to 30 psi.

The inert gas used for the conical shield 116 may be any inert gas including nitrogen, helium, neon, argon, krypton, xenon or a mixture thereof.

FIG. 3 illustrates an alternate embodiment of the rapid solidification apparatus 100. As illustrated in FIG. 3 the rapid solidification apparatus 100 further comprises a second source of inert gas 302. The second source of inert gas 302 is configured to provide a second conical shield 304 of inert gas surrounding the conical shield 116. The second source of inert gas 302 may be a plurality of second gas nozzles 306 that directs inert gas towards the movable chill body 102. The second conical shield 304 extends from the molten material nozzle 104 towards the movable chill body 102. The focal point of the second conical shield 304 may be at or proximate the movable chill body 102 and upstream of the point of contact between the stream of molten material 110 and the movable chill body 102. The second conical shield 304 removes oxidizing gas from the quench surface 108 of the movable chill body 102 before the stream of molten material 110 comes in contact with the quench surface 108.

In the embodiment, where a second conical shield 304 is provided, the focal point 118 of the conical shield 116 is at the stream of the molten material 110. In such embodiment, the gas nozzles 120 are located coaxial with the molten material nozzle 104. The second conical shield 304 may be pressurized. In an embodiment the second source of inert gas 302 is configured to pressurize the inert gas. In another embodiment, an external compressor (not shown) may be used for pressurizing the inert gas. In such embodiments, the external compressor is in fluid communication with the second source of inert gas 302. The pressure of the second conical shield 304 may be greater than or equal to 30 psi. The inert gas may be any suitable gas including but not limited to nitrogen, helium, neon, argon, krypton, xenon or a mixture thereof.

In an embodiment, the rapid solidification apparatus 100 further comprises a heating device 122. The heating device 122 compensates the cooling effect of the pressurized inert gas and prevents clogging of molten material nozzle 104 due to pre-mature freezing of the molten material at the molten material nozzle 104 and prior to contact of the molten material with the quench surface 108 of the movable chill body 102. The heating device 122 also prevents water condensation due to expansion of pressurized inert gas. The heating device 122 is placed between the molten material nozzle 104 and the source of inert gas 106. In accordance with an alternate embodiment, the heating device 122 may be placed on the molten material nozzle 104 between the molten material orifice 114 and the source of inert gas 106. The insulation provided between the heating device 122 and the inert gas nozzle 120 should be such that the inert gas is heated to prevent water condensation, but not overheated so that solidification rate of the rapid solidification apparatus is reduced.

In the embodiment, where the source of inert gas 106 is placed at a point away from the molten material nozzle 104 and in between the molten material nozzle 104 and the movable chill body 102, the heating device 122 is also placed on the source of inert gas 106 as shown in FIG. 2 to prevent water condensation due to expansion of pressurized inert gas.

INDUSTRIAL APPLICABILITY

The present disclosure discloses a rapid solidification apparatus 100. The rapid solidification apparatus 100 as disclosed comprises of a source of inert gas 106 that is configured to provide a conical shield 116 of pressurized inert gas around the stream of molten material 110. The conical shield 116 of pressurized inert gas extends from the molten material nozzle 104 towards the quench surface 108 with focal point 118 of the conical shield 116 at or proximate the quench surface 108. The conical shield 116 of pressurized inert gas completely surrounds the stream of molten material 110. This protects the stream of molten material 110 from oxidizing gases and prevents oxidation of the molten material. Further, as the conical shield 116 has a focal point 118 at or proximate the quench surface 108, this prevents any fresh air from being brought inside the conical shield 116. Thus, protecting the stream of molten material 110 from oxidizing gases.

In another aspect of the present disclosure, the conical shield 116 of inert gas has a focal point 118 upstream of the point of contact between the molten material and the movable chill body 102. This removes any oxidizing gas from the quench surface 108 of the movable chill body 102 before the molten material comes in contact with the quench surface 108, thereby preventing oxidation of the molten material.

In yet another aspect of the present disclosure, the pressurized conical shield prevents external air, especially air flow generated by moving chill roll from entering the shield and causing oxidation of the molten material. The pressurized shield further ensures removal of any residual gases on the quench surface that may result in oxidation of the molten material.

In yet another aspect of the present disclosure, the rapid solidification apparatus 100, has a second source of inert gas 302 that provides a second conical shield 304 around the conical shield 116. The second conical shield 304 also removes any oxidizing gas from the quench surface 108 of the movable chill body 102 before the molten material comes in contact with the quench surface 108 thereby preventing oxidation of the molten material.

In another aspect of the present disclosure, the rapid solidification apparatus has a heating device 122. The heating device 122 compensates the cooling effect of the pressurized inert gas and prevents clogging of molten material nozzle 104 due to pre-mature freezing of the molten material at the molten material nozzle 104 and prior to contact of the molten material with the quench surface 108 of the movable chill body 102. The heating device 122 also prevents water condensation due to expansion of pressurized inert gas. The insulation provided between the heating device 122 and the inert gas nozzle 120 should be such that the inert gas is heated to prevent water condensation, but not overheated so that solidification rate of the rapid solidification apparatus is reduced.

In yet another aspect the present disclosure, a method 400 for rapidly solidifying a molten material is disclosed. Referring to FIG. 4 the method 400 includes following steps. In step 402, one or more streams of molten material is directed from a source of molten material towards a moving chill body defining a quench surface. In step 404, a conical shield of pressurized gas is provided that extends from the source of molten material towards the quench surface with focal point of the conical shield at or proximate the quench surface. In accordance with an embodiment, the method 400 comprises pressurizing the pressurized inert gas to greater than or equal to 30 psi.

In an embodiment, the method 400 may comprise of directing pressurized inert gas towards the source of molten material and the chill body.

In an embodiment, the conical shield of pressured gas extends from the source of molten material towards the quench surface such that the focal point of the conical shield is upstream of the point of contact between the molten material and the chill body.

In an embodiment, the method may further comprise of providing a second conical shield of inert gas that surrounds the conical shield. The inert gas of second conical shield may be pressured. The second conical shield may have focal point at or proximate the chill body and upstream of the point of contact between the molten material and the chill body. In the embodiment, where a second conical shield is provided, the method comprises providing the conical shield at the stream of molten material. The method as disclosed protects the stream of molten material from oxidation. 

What is claimed is:
 1. A rapid solidification apparatus comprising: a movable chill body defining a quench surface; a molten material nozzle for directing one or more streams of molten material towards the quench surface; and a source of inert gas configured to provide a conical shield of pressurized inert gas around the one or more streams of molten material, the conical shield extending from the molten material nozzle towards the quench surface with focal point of the conical shield at or proximate the quench surface.
 2. A rapid solidification apparatus as claimed in claim 1 wherein the source of inert gas is a plurality of gas nozzles.
 3. A rapid solidification apparatus as claimed in claim 1 wherein the source of inert gas is attached to the molten material nozzle.
 4. A rapid solidification apparatus as claimed in claim 1 wherein the source of inert gas is configured to direct pressurized inert gas towards the molten material nozzle and the chill body.
 5. A rapid solidification apparatus as claimed in claim 1 wherein the rapid solidification apparatus includes a heating device.
 6. A rapid solidification apparatus as claimed in claim 1 wherein the source of inert gas is an angled nozzle ring.
 7. A rapid solidification apparatus as claimed in claim 1 wherein the focal point of the conical shield is upstream of the point of contact between the molten material and the chill body.
 8. A rapid solidification apparatus as claimed in claim 1 further comprising a second source of inert gas configured to provide a second conical shield of inert gas surrounding the conical shield.
 9. A rapid solidification apparatus as claimed in claim 8 wherein the second conical shield extends from the molten material nozzle towards the chill body with focal point of the second conical shield at or proximate the chill body and upstream of the point of contact between the molten material and the chill body.
 10. A rapid solidification apparatus as claimed in claim 9 wherein the focal point of the conical shield is at the stream of molten material.
 11. A rapid solidification apparatus as claimed in claim 1 wherein the movable chill body is a chill roll.
 12. A rapid solidification apparatus as claimed in claim 1 wherein the pressure of the pressurized inert gas is greater than or equal to 30 psi.
 13. A method of rapidly solidifying a molten material comprising: directing one or more streams of molten material from a source of molten material towards a moving chill body defining a quench surface; and providing a conical shield of pressurized inert gas around the one or more streams of molten material, the conical shield extending from the source of molten material towards the quench surface with focal point of the conical shield at or proximate the quench surface.
 14. The method of claim 13 comprising pressurizing the pressurized inert gas to greater than or equal to 30 psi.
 15. The method of claim 13 comprising directing pressurized inert gas towards the source of molten material and the chill body.
 16. The method of claim 13 wherein the focal point of the conical shield is upstream of the point of contact between the molten material and the chill body.
 17. The method of claim 13 further comprising providing a second conical shield of inert gas that surrounds the conical shield.
 18. The method of claim 17 further comprising pressurizing the inert gas of the second conical shield.
 19. The method of claim 17 wherein the second conical shield extends from the source of molten material towards the chill body with the focal point of the second conical shield at or proximate the chill body and upstream of the point of contact between the molten material and the chill body.
 20. The method of claim 19 wherein the focal point of the conical shield is at the stream of molten material. 